BEIJING (AFP) - Police in China's western Xinjiang region have accused a prominent Uighur academic detained since last week of being involved in "separatist activities", state media reported on Sunday.

Mr Ilham Tohti, an economist who teaches at the Central University for Nationalities in Beijing, has vocally criticised the Chinese government's policy towards his mostly Muslim Uighur minority.

The academic and his mother were taken on Wednesday 15 to an unknown location by several dozen police who seized their mobile phones and computers, his wife Guzaili Nu'er previously told AFP. The mother was released the following day.

Early on Sunday, the official Xinhua news agency reported that police authorities in Xinjiang said Mr Tohti "formed a separatist group" and "severely damaged the national security and social stability".

"Ilham Tohti organised a group with the disguise of his identity, colluded with leaders of overseas East Turkistan separatist forces, and sent followers overseas to engage in separatist activities," Xinhua said citing a statement from the municipal public security bureau in the Xinjiang regional capital Urumqi.

Last week, China's foreign ministry said Mr Tohti had been "criminally detained" because he was "under suspicion of committing crimes and violating the law".

The academic has been detained on a number of occasions in the past few years, including for more than a week in 2009 after his website Uighurbiz.net - an information site on Xinjiang in Chinese and Uighur - ran reports on riots in the region which killed around 200 people.

The vast western area has for years seen sporadic unrest by Uighurs, which rights groups say is driven by cultural oppression, intrusive security measures and immigration by Han Chinese.

Beijing attributes the unrest to religious extremists and separatism.

In late October, police said three Uighurs drove a vehicle into crowds of tourists opposite Beijing's Tiananmen Square, killing two people and injuring 40, before crashing outside the Forbidden City and setting their vehicle ablaze. All three attackers died.

Mr Tohti had warned against the temptation to stigmatise Uighurs after these events.

On Saturday, authorities said six people died in explosions and another six were shot dead in Xinjiang.